By now, we know that pollinators are important for our food sources… but what about the role native pollinators play in native plant communities?

Guidelines for pollinator gardens always recommend native plants over non-native and hybrids -- and it now seems for good reason.

As it turns out, recent studies show that there are negative impacts to pollinators and native plants when non-native and invasive species grow nearby.

Invasive Plants Impact Pollinator Species

Invasive plants can have a negative impact on certain pollinator populations.

One example is a relatively uncommon butterfly species in Pennsylvania, the West Virginia White butterfly (Pieris virginiensis), that uses native toothworts as its host plant.

Garlic mustard (Alliaria petiolata), an invasive plant that grows in the same habitat as the toothworts and is closely related, attracts the West Virginia White.

As the female chooses plants to lay its eggs, she can’t tell the difference between the two, and eggs are sometimes laid on garlic mustard.

The eggs laid on garlic mustard do not hatch, because the chemical compounds needed for development are not available -- resulting in reduced populations.

Invasive Plants Impact Pollinator’s Job

Pollinators can be generalists, pollinating many different species, or specialists, designed to pollinate only one species.

When a pollinator sticks its head or body into a flower, it accomplishes two things -- it gets nectar for food and unintentionally, picks up pollen.

Some pollinators are physiologically adapted to do both things for specific plant species.

If they select a species of flower that they aren’t designed to pollinate, they may only get the nectar and not pick up pollen.

A flower not pollinated will not produce seeds or fruit, and therefore the chance of reproducing is reduced.

Over time, this could reduce the number of plants in a population.

Invasive Plants Impact Pollinator Ecosystems

In the ecosystem, pollinators have many roles, and other than pollinating, they are also nutritious bird food.

The number of insects found feeding on native plants is greater than the number found on invasive plants.

More insects as bird food means an increase in the number of baby birds, and that leads to healthier and larger bird populations.

A recent study showed non-native plant species compete for pollinator services.

When a native loosestrife species (Lythrum alatum), and the non-native invasive purple loosestrife (Lythrum salicaria) were planted together and observed for pollinator visitation, it was documented that the presence of purple loosestrife reduced pollinator visitation and seed set in the native loosestrife species.

Additionally, visitation to both species by the same pollinator could cause a reduction in pollen quality and quantity in the native loosestrife.

This is one example of negative impact, but not necessarily applicable to all cases.

Both species grow in Pennsylvania and the native species is considered for endangered classification.

It is likely that, as more research is conducted, we will continue to reveal negative impacts that invasive plant species have on both pollinators and native plants communities.

NewsClips:

PennDOT Asks Public To Plant Pollinator Gardens In Erie

Olson: Honeybees Suffered High Losses Last Winter, Including In Toomey’s Backyard

Related Pollinator Week Articles:

Non-Native, Invasive Plant Species Are Ecologically Castrating The Landscape In PA, But There Is A Solution

House Passes Resolution Designating June 17-23 As Pollinator Week In PA

Bay Journal-Crable: PennDOT Hopes Plantings Will Put Pollinators On Road To Recovery

Penn State Extension: Planting Pollinator-Friendly Gardens - Pollinator Week June 17-23

DCNR Good Natured Blog: Hand Pollination Used For Rare Orchid When There's A Lack Of Pollinators

Pollinator/Native Plant Resources

There are lots of resources available to help property owners landscape with native plants, and now is the best time to start planning for Spring projects.  Here are just a few of the resources available--

-- DCNR Landscaping With Native Plants

-- Game Commission: Common Beneficial Plants Found In Wildlife Habitat

-- U.S. Fish & Wildlife Service: Native Plants For Wildlife Habitat And Conservation Landscaping

-- Chesapeake Bay Sustainable Landscape Professional Directory

-- Brandywine Conservancy: Forested Riparian Buffer Planting Guide

-- Audubon PA: Bird Habitat Recognition Program

-- National Audubon: Native Plants Database

-- Xerces Society For Invertebrate Conservation

-- Gardening For Butterflies: Penn State Extension

-- Planting For Pollinators: Penn State Extension

-- Center For Pollinator Research, Penn State

-- Pennsylvania Pollinator Protection Plan - Learn Why Pollinators Are At Risk In PA

-- Ernst Seeds - Pollinator Habitat Restoration

-- Million Pollinator Garden Challenge

You can also check with land trusts, watershed groups, PA Audubon and Trout Unlimited Chapters, county conservation districts or other groups near you to see how they can help.

Related Stories:

Senate Hearing: Non-Native, Invasive Plant Species Ecologically Castrating The Landscape, But There Is A Solution

Manada Conservancy Offers Native Plant Landscape Design Service [Recommended]

Feature: Recognizing The Value Of Native Plants For Pollinators - Dr. Doug Tallamy

Agriculture, Penn State Release PA Pollinator Protection Plan Recommendations

Pollinator Population Is Going Down In PA Due To Pesticides, Parasites And Pathogens

PennDOT Launches New Pollinator Habitat Plan; Adopt And Beautify For Pollinators Program For Citizens Who Want To Help

Sen. Yudichak, Cong. Barletta, Author Caroline Jones Celebrate The Launch Of We Saved The Bees And The Butterflies Children's Book

[Posted: June 20, 2019]

6/23/2019